Five accused September 11 plotters have been formally charged by US authorities and will face a military trial later this year. Here are short profiles of the group.
Al-Qaeda operative Khalid Sheikh Mohammed shortly after his capture, in Rawalpindi, Pakistan
Khalid Sheikh Mohammed, 46
A Kuwaiti-born Pakistani educated in the United States, he claims to be the mastermind of the September 11, 2001 attacks and a whole string of other crimes, including the beheading of US reporter Daniel Pearl in 2002. Known as KSM, Mohammed was waterboarded 183 times between his capture in Pakistan in March 2003 and his transfer to Guantánamo in September 2006.
Ramzi Binalshibh, 39
A citizen of Yemen, he co-rented a flat in Hamburg, Germany, with suspected 9/11 ringleader Mohammed Atta. US officials say he tried but failed four times to obtain a US visa to become a pilot-hijacker. Captured in Pakistan in September 2002, Binalshibh is accused of serving as the primary link between the hijackers in the United States and al-Qaeda leaders in Afghanistan and Pakistan during the eight months before the attacks. He was being treated with psychotropic drugs at Guantánamo.
Ali Abd al-Aziz Ali, around 35
A Pakistani raised in Kuwait who is Khalid Sheikh Mohammed's nephew and a cousin of jailed 1993 World Trade Center bomber Ramzi Youssef. Also known as Ammar al-Baluchi, he is believed to have played an important role in helping facilitate 9/11 logistics by transferring funds to US-based operatives and helping hijackers travel from Pakistan to the United States. He was captured in April 2003 in Pakistan.
Walid bin Attash, around 31
Born and raised in Saudi Arabia to Yemeni parents, he is accused of being the mastermind of the 2000 attack on the USS Cole destroyer in Yemen, which killed 17 US soldiers. Also known as Khallad, he lost his right leg during a 1997 battle in Afghanistan and supervised training at an al-Qaeda camp there where he trained two of the September 11 hijackers along with other operatives. Allegedly chosen by al-Qaeda leader Osama bin Laden at the outset to become a 9/11 hijacker himself, he was captured along with Ali Abd al-Aziz Ali in Pakistan in April 2003.
Mustapha Ahmed al-Hawsawi, 43
A Saudi associate of bin Laden accused of holding the group's purse strings in its first years of existence, and of having arranged funding for the September 11 plot. Both Al-Hawsawi and Ramzi Binalshibh are said to have served as a communications link between Khalid Sheikh Mohammed and the 9/11 hijackers. He was captured in Pakistan in March 2003, when special forces stormed the villa in which he was hiding along with Mohammed.